Abstract
BackgroundIn cases of Oxford unicompartmental knee arthroplasty (UKA), an increase in anteroposterior and medial-lateral length is usually disproportional when comparing AA and A-sized tibial components. Asynchronous increments may cause tibial keel impingement leading to complications.MethodsRadiographic measurements were performed in five patients with AA-sized tibial implants. The posterior cortex of proximal tibia had two angles recorded as ∠ M1 and ∠ M2. The minimum distance between the tibial component keel and outer margin of the posterior tibial cortex (mDKC) was measured, and the correlation between the preoperative posterior slope angle (PSA), ∠ M1, and mDKC was analyzed.ResultsAll patients showed an acceptable component positioning. Only one patient had an mDKC of < 4 mm that fulfilled the criteria for the posterior tibial cortex at risk. The patient had an increased PSA and ∠ M1 compared to other patients. A negative correlation was found between preoperative PSA and mDKC (r = − 0.935, p = 0.0193); and ∠ M1 and mDKC (r = − 0.969, p = 0.0032). However, no stem tip pain, periprosthetic fracture, or component loosening were observed.ConclusionsThe distance between the tibial keel and posterior tibial cortex was reduced in AA-sized patients with a large PSA and ∠M1; therefore, the risk of the tibial cortex injury should be considered.
Highlights
In cases of Oxford unicompartmental knee arthroplasty (UKA), an increase in anteroposterior and medial-lateral length is usually disproportional when comparing AA and A-sized tibial components
One patient had an mDKC < 4 mm which fulfilled the criterion for the posterior tibial cortex at risk
A negative correlation was found between the preoperative posterior slope angle (PSA) and mDKC (r = − 0.935, p = 0.0193); the ∠ M1 and mDKC (r = − 0.969, p = 0.0032) (Fig. 3)
Summary
In cases of Oxford unicompartmental knee arthroplasty (UKA), an increase in anteroposterior and medial-lateral length is usually disproportional when comparing AA and A-sized tibial components. Oxford unicompartmental arthroplasty (UKA) is one of the most successful surgical options for medial compartment osteoarthritis, catastrophic complications can occur and can be difficult to manage. Periprosthetic fracture and sinking of tibial components have been recognized as the most devastating complications. Precise bone cuts and adequately sized components are key to good results and prevent unnecessarily weakened tibia and uneven stress distribution [1]. During Oxford UKA, the tibial component overhang of 3 mm or more can cause soft tissue irritation and can severely compromise the outcome. An optimal match between tibial component and resected tibial surface results in flush edges with the cortical bone, which is the key factor for long-term good results
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